Some thoughts arise automatically in the mind, with no sense of control or mental effort; an example is what happens when we see the expression 2 + 2. Other thoughts are accompanied by the subjective experience of mental effort, and sometimes by a serial rule-governed process. This elementary duality is the core of many psychological theories developed in the last 25 years. I present a particular version, which builds on the metaphor of two distinct Systems in the mind: an automatic System 1 and an effortful System 2. System 1 can be identified with associative memory, and System 2 with the function of executive control. The characteristics of the two Systems and the interaction between them provide an interpretation of a large and diverse set of phenomena of judgment and choice that have been observed over the last 40 years of psychological research. In particular, the characteristics of System 1 explain both the marvels of successful intuition and the superficial, biased and overconfident thoughts and preferences that often govern human behavior.

Daniel Kahneman is Emeritus Professor of Psychology and Public Affairs at Princeton University. He studied Psychology and Mathematics in Jerusalem, earned his PhD in Berkeley 1961 and taught in Harvard, British Columbia and Berkeley before becoming Eugene Higgins Professor of Psychology in Princeton in 1993. He is renowned for his works on on the psychology of judgment and decision-making. In 2002, Daniel Kahneman was awarded the Nobel Prize in Economic Sciences "for having integrated insights from psychological research into economic science".

Image: Daniel Kahneman